Optimizing query ,sybase

rbhargaw
rbhargaw used Ask the Experts™
on
Is there a better way to right this query which increase optimization?

select table1.id 'MCN'
      ,table1.LastName+', '+table1.FirstName 'Name'
      ,PTList.noteDate 'LastDocumented'
      ,table1.patientid
      ,(
      select DisplayValue from table3
            where selectionvalueid = table1.gender
       ) 'Gender'
       
     ,table1.dateofbirth
     
     ,PTLIST.notepadid
     
     ,PTLIST.note
 from
       
       (
           select distinct table2.patientid, notepadid, noteDate, note
         
           from  table2
           
           inner join table5
              on table5.PatientId = table2.patientid
             
           inner join table4
              on table4.TxEventId = table5.TxEventId
             
           where closedDate is null
             and noteType = (
                               select selectionvalueid from  table3
                              where code = 'NoteType_Pending'
                             )
                             
             and    
             
             case --Calculate coordinator id based on whether or not the transplant has occurred
                     when table4.TxDate is null
                     then table4.PreTxCoordinator
                            else table4.PostTxCoordinator
                        end  =   {0}       --Parameter              
        )
        PTList
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Can you post structure of your tables, indexes and number of rows in tables ?

And it seems like your query is not complete - you use table1 in the first part, but there is no table1 in FROM clause.
Principal Consultant
Most Valuable Expert 2012
Commented:
I am suspicious of the distinct in the derived table. Why is it there? Why use a derived table at all? You don't join to it in any way. Flatten everything in it to the outermost query. If you need the distinct to eliminate duplicates, you haven't put enough joins and/or WHERE clauses in.

Likewise I don't see any reason why your correlated subquery on table3 couldn't be written as a regular join.
rbhargawFounder

Author

Commented:
Thanks Joe, I will remove the derived table,  how to deal with the case statement?
Joe WoodhousePrincipal Consultant
Most Valuable Expert 2012

Commented:
I don't think you can change the CASE, but I don't think you need to, CASE isn't expensive.
rbhargawFounder

Author

Commented:
Not enough joins in the table and hence working on that. The answers points to right direction

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